This invention relates to bag making machines and more particularly to improvements in bag bottom forming apparatus for such machines.
In bag making machines to which the present invention is particularly applicable, a web of sheet material, such as paper for example, is progressively fed into the machine and formed into a tube. Gussets are formed along the opposing side edges of the tube and at preselected intervals, the tube is severed, notched and slit preparatory to bottom-forming operations upon the successive blanks. Next, the tubular bag blank is scored with a pair of parallel score lines adjacent the leading end thereof, which are included on the bottom layer as well as the upper layer of the blank. The tube is then passed to the opening cylinder and finishing drum, the finishing drum having fingers that close on the first score line on the lower or bottom layer of the tube gussets. The tube moves forward to the opening cylinder that has opening fingers that close on the first score line of the top or upper layer of the tube. These fingers open the tube to make a bottom formation, and thereafter the opening finger releases the top part of the tube from about 3/8ths inch to about 1/2 inch below the bottom formers. The bottom formers then complete the bottom formation and flatten it against the drum so that the upper layer is folded back on itself along the score line to thereby provide a leading flap of bottom layer extending from one of the other score lines of the upper layer. Thereafter, adhesive or paste is applied to the surfaces of the leading flap and overlying panel portions. The trailing flap is then folded along the leading score lines of the upper layer forwardly and upon the panel portions and, consequently upon the exposed adhesive. Subsequently, the leading flap is folded rearwardly along its leading score line so that it will not only adhere to the panels but to the outer surfaces of the trailing flap as well. The bag blank is thus formed into a finished bag, which is then discharged from the machine.
An object of the invention is to provide a new and improved bottom forming device which may be easily applied to existing types of bag forming machines without greatly altering the present construction thereof and which is relatively simple, compact, convenient, practical, and inexpensive.
Another object of the invention is to provide an improved bottom forming device which, before the opening cylinder fingers release the top part of the tube, the bottom formers are in contact with the open tube, thereby causing the open tube to break on the first and second score lines at the same time the bottom is formed in a rolling motion instead of a break-down motion as was effected with prior commerical machines.
Another object of the invention is to provide an improved bottom forming device which simplifies the adjustment procedure, which has complete control of the bottom formation, at all times, which increases the machine speed from about 50 to about 75 bags per minute, which avoids air traps, and which makes quality bags at a substantially lower rate of speed than heretofore, thereby reducing the wastage during start-up.
Thus, the present invention involves a novel combination of features combined in such a way as to afford a very efficient and effective solution to the difficulties encountered with the prior art, as will become apparent as the description proceeds.
In order to accomplish the desired results, this invention provides in one form thereof, a new and improved bottom forming device for a bag making machine comprising a pair of bottom formers, each bottom former being of plate-like construction and having a vertical side portion and a horizontal top portion connected along a fold line. According to one aspect of the invention, the horizontal top portion has an inner edge which has an elongated portion extending inwardly and rearwardly. According to another aspect of the invention, the vertical side portion on upper front edge which extends upwardly and rearwardly, a lower front edge which extends downwardly and rearwardly, and said upper front edge and said lower front edge meeting to form a pointed front edge. According to still another aspect of the invention, the vertical side portion has a medial lower edge portion that is upwardly arcuately bowed.
There has thus been outlined rather broadly the more important features of the invention in order that the detailed description thereof that follows may be better understood, and in order that the present contribution to the art may be better appreciated. There are, of course, additional features of the invention that will be described more fully hereinafter. Those skilled in the art will appreciate that the conception on which this disclosure is based may readily be utilized as the basis of the designing of other structures for carrying out the purposes of this invention. It is important, therefore, that this disclosure be regarded as including such equivalent construction as do not depart from the spirit and scope of the invention.